Chemical composition and antibacterial activity of essential oils from six Moroccan plants

Abstract

The essential oils (EOs) of six plants (Artemisa herba alba, Rosmarinus officinalis,Ocimum basilicum, Lavandula officinalis, Mentha viridis and Mentha piperita) widely distributed in Morocco were isolated and their chemical composition was investigated by gas chromatography-mass spectrometry (GC/MS). These EOs were tested in vitro against four pathogenic bacterial strains (Enterococcus faecalis, Escherichia coli, Klebsiella pneumoniae and Streptococcus D) and we determined the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of each EO. The oils of various plants showed high activity against all tested bacteria (MIC≤10 µL/ml), of which K. pneumoniae was the most sensitive strain (MIC≤5 µL/ml). In addition, the oil from M. viridisL. which contained high pulegone concentration (45%) exhibited a very interesting antibacterial activity against all the bacterial strains (MIC 2.5 µL/ml) and (MBC 2.5 µL/ml). The UV-visible study on the release of material absorbing at 260 nm showed significant leakage of cytoplasmic contents, indicating damage to the bacterial cell membrane integrity. Thus, these results indicate that the EOs represent a potential source of natural antibacterial substances that may be used against pathogenic systems. Key words: Artemisia herba alba, Rosmarinus officinalis, Ocimum basilicum, Lavandula officinalis, Mentha viridis, Mentha piperita, essential oil composition, pulegone, antibacterial activity.